Biomaterials 26 (2005) 1329–1336 Development of highly reactive mono-(meth)acrylates as reactive diluents for dimethacrylate-based dental resin systems Hui Lu a , Jeffrey W. Stansbury a,b , Jun Nie c , Kathryn A. Berchtold d , Christopher N. Bowman a,b, * a Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA b Department of Restorative Dentistry, University of Colorado Health Sciences Center, Denver, CO 80262, USA c College of Chemistry, Wuhan University, Wuhan, Hubei 430072, China d Los Alamos National Laboratory, Materials Science and Technology Division, MS E549, Los Alamos, New Mexico 87545, USA Received 9 February 2004; accepted 17 April 2004 Available online 24 June 2004 Abstract Reactive diluents such as triethyleneglycol-dimethacrylate (TEGDMA) have been widely used with bisphenol-A-glycidyl- dimethacrylate (Bis-GMA) to achieve restorative resins with appropriate viscosity and higher conversion. However, additional water sorption and polymerization shrinkage were also introduced. The aim of this work is to investigate whether the cure and material properties can be improved in dental resins containing novel mono-(meth)acrylates as reactive diluents so that these Bis-GMA-based copolymers have reduced polymerization shrinkage but higher overall double bond conversion. Several ultra-high- reactivity mono-(meth)acrylates that contain secondary functionalities have been synthesized and investigated. The polymerization rate and double bond conversion were monitored using photo-FTIR. Polymerization shrinkage, dynamic mechanical analysis, and flexural strength were characterized. Compared with the Bis-GMA/TEGDMA control, the Bis-GMA/mono-methacrylate systems studied showed higher final conversions, faster curing rates, and decreased polymerization shrinkage. Our optimum system Bis-GMA/morpholine carbamate methacrylate achieved 86% final conversion (vs. 65%), a polymerization rate 3.5 times faster, and a 30% reduction in polymerization volumetric shrinkage. These results indicate that certain highly reactive, novel mono- (meth)acrylates possess very promising potential to replace TEGDMA as reactive diluents and can readily be applied to develop superior dental resins. r 2004 Elsevier Ltd. All rights reserved. Keywords: Dental resins; Photopolymerization; Reactive diluent; Volumetric shrinkage 1. Introduction Visible light-activated polymeric composites are now routinely used as filling materials for dental restorations, mostly because of their esthetic merit and ‘‘cure-on- command’’ feature. Since its first development in 1960s, the ‘‘Bowen resin’’ (2,2-bis[4-(2-hydroxy-3-methacrylox- yprop-1-oxy)phenyl]propane or Bis-GMA) is still the most commonly used base resin in current dental restorative composite formulations [1]. The advantages of using Bis-GMA include its high modulus and glass transition temperature, low volatility, and relatively low polymerization shrinkage. However, the extremely high viscosity of Bis-GMA requires dilution with 20–35wt% low-viscosity monomer, such as triethyleneglycol di- methacrylate (TEGMDA) or ethyleneglycol dimetha- crylate (EGDMA), to achieve easier handling, higher filler loading and greater extent of polymerization [1,2]. Although the ultimate double bond conversion of Bis- GMA/TEGDMA has been increased to 60–75% (com- pared with 40–50% of the neat Bis-GMA resin [3]), some drawbacks also result from the addition of TEGDMA, such as increased polymerization shrinkage [3,4], water absorption [5], and potential adverse effects ARTICLE IN PRESS *Corresponding author. Department of Chemical and Biological Engineering, Engineering Center, ECCH 111, University of Colorado, Boulder, CO 80262, USA. E-mail address: christopher.bowman@colorado.edu (C.N. Bowman). 0142-9612/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2004.04.041